This invention relates, in general, to electronic warfare systems and, more specifically, to active radar jamming systems.
Active radar jammers are used in the field of electronic countermeasures to confuse or counter the system originating the radar signals. In some situations, it is desirable to return signals to the radar system which are exact copies of the arriving radar signal. In other situations, it is desirable to return signals to the radar system which have characteristics other than that of the received radar signal. Frequently, this type of returned signal is in the form of RF noise for the purpose of jamming the radar system. In addition to the type of the RF signal desired to be transmitted by the jamming system, the angle-of-arrival of the radar signal and the steering of the antenna beam when transmitting from the jamming system are also important considerations. In addition, the type of signal received by the jamming system is of concern, such as whether the radar signal received by the jamming system contains phase coding or chirp modulation.
In order to achieve these capabilities and functions according to the prior art, many separate subsystems and discrete elements were necessary to perform many of the functions of the jamming system, such as signal reception, transponder or repeater operation, noise generation, angle of arrival determination, and transmit antenna steering. The use of separate subsystems presents a cost and reliability consideration in the manufacture and operation of such devices. In addition, such separate subsystems are usually dedicated to a particular function, and modifying or programming these subsystems for different functions is not easily accomplished.
It is desirable to use a digital radio frequency memory (DRFM) for the purpose of obtaining and storing the data from the radar signal. U.S. Pat. Nos. 3,947,827 and 3,991,409 teach the use of an DRFM in electronic countermeasure systems. While these patents disclose or mention the use of an DRFM in connection with electronic countermeasure systems, they do not teach the use of an DRFM for the purposes disclosed and claimed by the present invention.
It is desirable, and it is an object of this invention, to provide a radar jamming system wherein the requirement for separate subsystems as taught by the prior art are mostly eliminated, and wherein the capabilities of the jamming device to detect and originate suitable signals are enhanced by the ability to better adapt to the prevailing conditions and requirements.